1. Field of the Invention
The present invention relates generally to a seal system for the covers of an outboard motor and, more particularly, to a seal system which uses engine crankcase pressure to inflate a hollow tube seal arrangement to more positively seal the motor covers against intrusion of ambient water.
2. Description of the Related Art
It is a common practice to enclose an outboard motor with an assembly of cowls or motor covers to protect the engine components from ambient water intrusion and the harmful effects thereof Particularly the effects of seawater can result in large deposits of corrosive salt on engine components due to evaporation of the seawater by engine heat. It is also common practice to provide an upper motor cover which is readily removable for servicing of the engine. Conventionally, it has been the practice to employ compression-type members to seal motor covers. However, sealing is complicated by the fact that engine parts move relative to each other due to engine vibration, due to hydrodynamic forces which can deflect mating parts, and due to vacuum under the motor covers which tends to deflect the covers inwardly. All of these forces can cause compression seals to open, allowing water to intrude into the engine compartment.
In an effort to provide for effective sealing with compression type seals it has been necessary to provide quite high sealing forces. For example, with a conventional upper motor cover it is common to apply a pressing force in the range of 100 to 200 kilograms to the seal member in assembling the upper cover in order to obtain satisfactory sealing. Such high compressive force can cause undesirable distortion of the cover. In addition, in order to provide the necessary sealing force a latch mechanism must be used which can be large and quite unsightly.
The problems associated with satisfactory sealing of motor covers are discussed, for example, in U.S. Pat. No. 5,135,239 issued to Kato et al. In that patent, Kato et al. propose a seal which comprises a base portion for affixing the seal to the motor cover. A seal portion is also provided for sealingly engaging the tray which extends beneath the engine. An intermediate portion integrally connects the base portion with the seal portion and the intermediate portion is deflected by bending upon assembly of the cover to the tray for sealing engagement of the seal portion without necessitating compression thereof.
While the seal system as just described provides some improvement in the sealing of outboard motor covers, it is desirable to provide a system which even more positively seals motor covers to avoid water intrusion in the face of the aforementioned engine vibration and hydrodynamic forces and effects of engine vacuum conditions. It is further desirable to provide such a seal system which allows the associated motor covers to be readily removed for servicing of the engine. Still further, it is desirable to provide such a seal system which is cost effective to manufacture and implement, thus avoiding excessive expense to the ultimate motor purchaser.